2016ApJ...833...79W

The hyperluminous X-ray source (HLX-1, peak X-ray luminosity ∼10⁴² erg s^–1) near the spiral galaxy ESO 243-49, which underwent recurrent outbursts within a period of ∼400 days, is possibly the best candidate for an intermediate mass black hole (IMBH). The physical reason for this quasiperiodic variability is still unclear. We explore the possibility of radiation-pressure instability in the accretion disk by modeling the light curve of HLX-1, and find that it can roughly reproduce the duration, period, and amplitude of the recurrent outbursts in HLX-1 with an IMBH of ∼10⁵ M_☉. Our result provides a possible mechanism to explain the recurrent outbursts in HLX-1. We further find a universal correlation between the outburst duration and the bolometric luminosity for the black hole (BH) sources with a very broad mass range (e.g., X-ray binaries, HLX-1, and active galactic nuclei), which is roughly consistent with the prediction of radiation-pressure instability of the accretion disk. These results imply that "heartbeat" oscillations triggered by radiation-pressure instability may appear in different-scale BH systems.